The present invention relates to a device for driving and thus rotating a disk (hereinafter referred to as "a disk drive device") which is incorporated in a disk apparatus.
A conventional disk drive device of this type has a structure such as that disclosed in, e.g., Japanese Patent Unexamined Publication No. 64-78462. To describe the outline of the conventional device, a rotary plate is mounted on a rotary drive shaft and integrally rotatable therewith. A swingable lever has its proximal end portion pivotally supported by the lower surface of the rotary plate in such a manner that the lever is also movable in the axial direction of the rotary drive shaft. The swingable lever is urged by a spring toward the rotary plate. A drive pin is provided on a distal end portion of the swingable lever and extends through a hole formed in the rotary plate and also through another hole formed in a magnet mounted on the rotary plate so as to magnetically attract a disk.
When a disk is placed on the rotary plate with a central hole of the disk fitted onto the rotary drive shaft, the disk is magnetically attracted by the magnet. In this condition, a drive pin engagement hole formed in the disk at a position eccentric to the center of the disk is not aligned with the drive pin. Therefore, the drive pin is pushed downward by the disk, so that the drive pin and the swingable lever are lowered from the disk against the force of the spring. When the rotary drive shaft is rotated by a motor of the disk apparatus, the rotation causes the rotary plate and the swingable lever to rotate. The disk, however, is held by a magnetic head of the apparatus and does not rotate until the drive pin engages with the drive pin engagement hole of the disk. This engagement causes the torque of the rotary plate to be transmitted through the drive pin to the disk, thereby causing the disk to rotate.
In the conventional disk drive device, the swingable lever is, as described above, supported by the lower surface of the rotary plate in such a manner as to be movable in the axial direction of the rotary shaft so that the drive pin of the swingable lever is engageable with the drive pin engagement hole of the disk. This arrangement requires clearances to be provided in order to prevent unnecessary contact between the swinging lever and other component parts, thus making it impossible to reduce the thickness of the entire device. The conventional device has another drawback that a costly spring for applying spring force to the swinging lever is required.